Brown Bears at Hidden Falls Fish Hatchery on Baranof Island, SE Alaska: 7-17-18

Even though grizzlies are considered a subspecies of brown bear, the difference between a grizzly bear and a brown bear is fairly arbitrary.  In North America, brown bears are generally considered to be those of the species that have access to coastal food resources like salmon and are therefore larger.  Grizzly bears live further inland and typically do not have access to marine-derived food resources and are therefore smaller than brownies.

Besides habitat and diet, there are physical and (arguably) temperamental differences between brown and grizzly bears.

Large male brown bears in Katmai can routinely weigh over 1,000 pounds in the fall.  In contrast, grizzly bears in Yellowstone National Park weigh far less on average.